Hydrocarbon conversion process improvements

ABSTRACT

Improvements in previously disclosed methods of and apparatuses for converting alkanes, alkenes, and aromatics to olefins, alcohols, ethers, and aldehydes includes: safety improvements, use of alternative feedstocks, process simplification, improvements to the halogenation step, improvements to the reproportionation step, improvements to the solid oxide reaction, improvements to solid oxide regeneration, improvements in separations, maintenance, start-up, shut-down, and materials of construction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 12/692,831 filed Jan. 25, 2010 now U.S. Pat. No. 7,838,708, which is a continuation of U.S. patent application Ser. No. 11/098,997 filed Apr. 5, 2005 now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 10/430,240 filed Aug. 19, 2003 now U.S. Pat. No. 7,161,050, which is a continuation-in-part of prior application Ser. No. 10/365,346 filed Feb. 12, 2003 now abandoned, which is a continuation of prior application Ser. No. 10/298,440 filed Nov. 19, 2002, abandoned, which is a continuation-in-part of prior application Ser. No. 10/208,068, filed Jul. 29, 2002, abandoned, which is a continuation-in-part of prior application Ser. No. 10/054,004 filed Jan. 24, 2002, now U.S. Pat. No. 6,486,368, which is a continuation-in-part of prior application Ser. No. 09/951,739, filed Sep. 11, 2001, now U.S. Pat. No. 6,465,696, which is a continuation-in-part of application Ser. No. 09/886,078 filed Jun. 20, 2001, now U.S. Pat. No. 6,472,572.

CLAIM OF PRIORITY

Applicant claims priority based on provisional patent application Ser. No. 60/559,844, filed Apr. 6, 2004.

TECHNICAL FIELD

This invention relates generally methods and apparatuses for synthesizing olefins, alcohols, ethers, and aldehydes from alkanes, alkenes, and aromatics, and more particularly to specific improvements in the methods and apparatuses disclosed in the patents and patent applications identified herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The present application comprises a continuation-in-part of application Ser. No. 10/430,240, the disclosure of which is incorporated herewith by reference as if set forth herein. The present invention comprises specific improvements in and to the methods and apparatuses disclosed and described in the patents and patent applications identified herein, specifically including:

Safety Improvements;

Use of Alternative Feedstocks;

Process Simplification;

Improvements to the Halogenation Step;

Improvements to the Reproportionation Step;

Improvements to the Solid Oxide Reaction;

Improvements to Solid Oxide Regeneration;

Improvements in Separations;

Maintenance;

Start-up;

Shut-down;

Materials of Construction.

DETAILED DESCRIPTION

Safety Improvements:

1. The safety of the process may be improved by shipping the halogen in solid halide form. Some specific variations include:

-   -   a. The solid may be one of the solids that will be used in the         process. One advantage is that separate halide liberation         equipment may be avoided. The solid may be regenerated using         air, oxygen, and/or oxygen-containing gas in the process         equipment.     -   b. The solid may also be a solid that is not used in the         process, but rather a solid which is inexpensive, relatively         non-toxic, able to liberate halide at lower temperature,         liberates halide with heating rather than oxidation, less         hygroscopic, less corrosive in solid form, less corrosive to         regenerate, less volatile, more dense, containing a higher         halogen content, disposable, and/or otherwise more convenient         for shipping. Examples include:         -   i. Copper chloride, copper bromide, or copper iodide may be             used for the shipment of chlorine, bromine, or iodine due to             relatively low cost of copper relative to some other             materials.         -   ii. Copper halides may be used for shipment for processes in             which the reactive solid contains nickel, chromium, lead,             cobalt, or other potentially toxic elements.         -   iii. Calcium bromide may be used to ship bromine for use in             a process using a cobalt-containing metal oxide since cobalt             bromide readily forms highly hydrated species.         -   iv. Copper chloride, copper bromide, or copper iodide may be             used for the shipment of chlorine, bromine, or iodine since             copper halides may be easily regenerated with air, oxygen,             or oxygen containing gas at temperatures below those             required to regenerate other solids.         -   v. Copper (II) bromide may be used to ship bromine since             bromine may be liberated by heating without oxygen.         -   vi. Copper bromide may be used to ship halide for processes             using iron-containing materials since iron bromide is             hygroscopic, potentially volatile, and potentially             corrosive.         -   vii. Pure copper halide may be used to ship halide for             processes using a supported metal oxide. Such a choice will             eliminate the need to transport the inert support.         -   viii. Carbon tetrabromide may be used with combustion of             this material either in dedicated equipment or within a             process unit, generating bromine and carbon dioxide. Such a             solid is disposable, thereby eliminating the requirement of             returning the solid oxide to a processing facility.     -   c. The solid may also be a solid that is not used in the process         so that the solid used may be shipped in oxide form, which may         be more stable, less likely to sinter, dissolve, adsorb (or         absorb) water (or other contaminants), or fracture.     -   d. As the solid used in the process can hold substantially more         bromine than the optimum level for use in the process, the solid         could be shipped to an operating facility with a relatively high         level of bromine that could be used to make up the small amount         of bromine that may be lost during normal operation of the         process.

2. The safety of the process may be improved by shipping the halogen in liquid halide form. The use of liquid may minimize solids handling operation and associated particulate hazards. Liquid may also be easier to handle.

-   -   a. Specifically, boron tribromide may be used with oxidation to         boron oxide liberating bromine.

3. The safety of the process may be improved by shipping the halogen in liquid alkyl halide form. The use of liquid halides may minimize solids handling operation and associated particulate hazards. The use of liquid halides may also be easier to handle. The shipment of alkyl halide may be particularly useful for the startup of the plant and may also provide a convenient and safe way to introduce make-up halide.

4. The safety of the process may be improved by the placement of hygroscopic metal halides in selected reactors provided with a sink for water in the event of a process upset. Many metal halides are hygroscopic and will react with water to form hydrates, minimizing corrosion.

-   -   a. The metal halides may be selected and placed so that they are         molten in the hydrated form and easily removed.     -   b. The metal halides may be selected based on a low melting         temperature so that they can be pumped into the process in the         event of an upset.

5. The bromine inventory may be reduced by utilization of the bromine separation apparatus (typically following the regeneration reactor) as the reservoir for bromine for introduction into the alkane bromination reactor or other necessary step involving bromine. This reservoir of liquid bromine will have sufficient capacity to maintain adequate pump priming and allow bromine to be pumped as a liquid rather than using more costly compressors.

6. Reactive metal oxide traps at all process vents for use in normal and emergency operations may be used to insure against release of any and all organic-bromides. These metal oxides may be regenerated to recover bromine.

7. The safety of the process may be enhanced by the use of a solid oxide to dispose of halogenated organic streams and recovery of halide by conversion to carbon dioxide, water, and solid halide. The solid oxide may be regenerated by reacting the solid halide with oxygen, liberating halogen for recycle to the process.

-   -   a. One example is the use of CuO or CuZrO₃ to convert vinyl         bromide to carbon dioxide, water, coke, and CuBr or CuBrZrO₂.         Use of Alternate Feedstocks

The above-identified processes may be useful and particularly valuable with feedstocks containing otherwise difficult to separate components. The halogenation chemistry may facilitate the reactive separation of various streams including:

1. The use of steams containing alkane and olefin of the same carbon number.

-   -   a. The olefin may be converted with molecular halogen or solid         halide to the 1,2-dihalide for use as a feedstock to an epoxide         process. The 1,2-dihalide will be easy to separate from the         alkane. Examples include:         -   i. Converting the propylene in a stream containing propane             and propylene to 1,2-dibromopropane and subsequently to             propylene oxide. The 1,2-dibromopropane is formed by             reacting the mixed hydrocarbon stream with bromine, most             preferably at low temperatures where little appreciable             reaction with propane occurs. Separation of propane from             propylene is required in many existing plants including             ethylene plants and is considered one of the most difficult             separations in the chemical industry.     -   b. The olefin may be converted with wet halogen to halohydrin         for use as a feedstock to an epoxide process. The halohydrin         will be easy to separate from the alkane. Examples include:         -   i. Converting the propylene in a stream containing propane             and propylene to the bromohydrin and subsequently to             propylene oxide. The propylene is converted by passing the             hydrocarbon stream through bromine water.     -   c. The olefin may be converted with hydrogen halide to form the         monohalide for use as a feedstock in an olefin, alcohol,         epoxide, aldehyde, ketone, or other process. The halide will be         easy to separate from the alkane. Examples include:         -   i. Converting olefin in a gasoline feed to alkyl halide by             reacting with hydrogen halide to form alkyl halide. The             alkyl halide can be easily removed, leaving olefin-depleted             gasoline.         -   ii. Converting butenes to butyl halides in a mixed feed of             butanes and butenes. The butyl halides may be coupled to             products containing eight carbon atoms for use in gasoline.

2. The use of streams containing branched and linear alkanes resulting in product streams enriched in branched and/or linear molecules.

-   -   a. Branched alkanes containing tertiary carbon may be         selectively halogenated to alkyl halide and separated, leaving a         stream enriched in linear alkane. Examples include:         -   i. Depletion of the branched content of detergent-range             alkanes by reaction with halide, resulting in greater             reactivity with the branched alkanes to branched alkyl             halides. Following separation of the branched halides, the             remaining stream is enriched in linear alkane. The stream             rich in branched halides may be dehydrohalogenated either             catalytically or using a solid oxide to create a stream rich             in branched olefin for hydroformylation and conversion to             branched alcohols.     -   b. Branched alkanes containing tertiary carbon may be         selectively halogenated to alkyl halide. Following separation,         the halide stream will inevitably contain some non-branched         halides. By selectively dehydrohalogenating the tertiary         halides, a stream containing a very high fraction of branched         olefins can be separated from the remaining halides. The         selective dehydrohalogenation may be conducted thermally, using         a catalyst at temperatures below those required for secondary         alkyl halide dehydrohalogenation, or using a solid oxide         cataloreactant at temperatures below those required for         secondary alkyl halide dehydrohalogenation. Dehydrohalogenating         the remaining halides will leave a stream enriched in linear         olefins.

3. The use of streams containing multiple types of branched molecules resulting in product streams enriched or depleted in molecules containing a certain type or amount of branching:

-   -   a. Streams containing linear, mono-branched, and         multiply-branched alkanes may be enriched or depleted in         multiply-branched product by halogenating the multiply-branched         alkanes to multiply-halogenated separation. The         multiply-halogenated and/or mono-halide species may be easily         separated. Following the desired separation of the         non-halogenated, mono-halogenated, and multi-halogenated         species, and dehydrohalogenation of the halides, the various         streams may be recombined to generate the desired branching         composition.     -   b. Streams containing branched alkanes with and without multiple         branching at a single carbon (quaternary carbon) may be depleted         in these quaternary carbon-containing species by halogenating         the branched alkanes without the quaternary carbon, separating         these halides, and dehydrohalogenating. The result will be         streams rich in branched olefins without quaternary carbon and         alkanes with quaternary carbon.

4. The use of streams containing trace amounts of impurities that are more reactive than the desired alkane reactant:

-   -   a. Alkane streams containing aromatics, alcohols, olefins,         aldehydes, ketones, sulfides, sulfates, or other reactive         molecules may be halogenated at low temperature to selectively         halogenate the impurities for removal.     -   b. Streams of mixed alkanes (e.g. natural gas, refinery streams)         may be differentially halogenated based on differing rates of         halogenation and subsequently reacted with metal oxides at lower         temperatures where the non-halogenated alkanes would pass         through without reaction.

5. The use of streams of mixed alkane and olefin in coupling processes. Streams containing alkanes and olefins may be used to produce products of higher carbon number. Several process variations may be employed:

-   -   a. A process with:         -   i. Olefin hydrohalogenation in the presence of the alkane;         -   ii. Separation of the resulting alkyl halide from the             alkane;         -   iii. Halogenation of Alkane;         -   iv. Separation of the resulting alkyl halide from the             alkane;         -   v. Recycle of alkane;         -   vi. Feed of the alkyl halide to the coupling reactor.     -   b. Several variations of (a) may be employed:         -   i. Specifically, step ii (separation of alkyl halide after             hydrohalogenation) may or may not be omitted.         -   ii. The alkane may or may not be separated from the alkyl             halide (step iv).         -   iii. Reproportionation chemistry may or may not be employed.         -   iv. The olefin and alkane may be separated at the beginning             of the process.         -   v. Halogenation may precede hydrohalogenation, particularly             if high temperature is employed to hinder addition of             halogen to the olefin.         -   vi. The hydrogen halide used for hydrohalogenation may or             may not be the same formed in the halogenation step.             Process Simplification

1. The halogenation and solid oxide reaction steps may be conducted in the same unit:

-   -   a. The halogenation and solid oxide reaction may be         simultaneous.     -   b. The halogenation may occur first by varying the contacting of         the hydrocarbon, halogen, and solid oxide.

2. The halogenation, solid oxide reaction, and solid oxide regeneration may be conducted in the same unit by introducing hydrocarbon and oxygen to a solid halide or solid halide-oxide combination. The oxygen will regenerate the solid halide generating hydrocarbon halide and solid oxide, the hydrocarbon halide will react with the oxide, generating product. Variations include:

-   -   a. Periodic switching of the direction of feed to the reactor to         minimize halogen migration from the reactor. Examples include:         -   i. Coupling methane to heavier products by cofeeding methane             and oxygen over a metal-halide-containing solid.

3. The solid oxide reaction and product separation may be conducted simultaneously when the product is lighter then the reactant the reaction is conducted in a liquid phase reactor under conditions where the product is a vapor and leaves the reactant mixture.

4. Reacting the halide-containing regeneration effluent with olefin to form dihaloalkanes to reduce the energy required for and equipment size in the halide recovery.

5. Reacting the alkane over selected metal-halides in the regeneration step to form the alkyl-halide and a metal-hydride. This would also be a safety improvement and eliminate the need for halogen separation. Materials include but are not limited to halides of boron, nickel, iron, and their mixtures as well as carbon based materials (e.g. C60).

6. Operation of the halogenation process at high halogen:alkane ratio for the feed at temperatures and pressures to maximize the production of monohalo-alkanes at 100% alkane conversion. The alkane feed may be mixed. The products which will contain multiply-halogenenated species and haloacid which may be passed directly over a metal oxide bed to produce a mixture of products dependent upon the reaction conditions will be produced which will be condensed together and separated in the liquid phase by a combination of distillation and phase separation.

7. The use of a hydrogenation step to recover the over-halogenated products by reducing the halogenation to the desired degree. The use of such a step will allow for higher per-pass conversion in the halogenation step. Catalysts may be used, including but not limited to Pd, Pt, Ru, Ni, Au, Cu, and their alloys.

8. Controlling the amount of hydrogen halide added to a metal oxide reactor in order to generate the heat required for an endothermic reaction.

9. The use of hydrogen halide formed in the halogenation step for conversion of byproducts or products into more useful compounds.

-   -   a. For example, HBr could be used to hydrobrominate         vinylbromide, a common undesirable by-product resulting from HBr         elimination from dibromoethane back to same (or any higher         vinylbromide equivalent to the corresponding dibromoalkane) . In         another example, HBr could be used in the acidic cleavage of         ethers into alcohols and alkylbromides, the former increasing         the yield of the desired alcohol product and the latter being         recycled to the educt stream for reaction on the metal oxide.         Improvements to the Halogenation Step

1. Improvements in selectivity to desired multiply-halogenated isomers through isomerization of the multiply-halogenated species formed by halogenation. Examples include:

-   -   a. Forming dihalides dehydrohalogenating the dihalides, and         rehydrohalogenating to form the desired isomers. The         rehydrohalogenation may be conducted using process conditions         different from the initial halogenation to enhance yield of the         desired isomer. The process conditions varied may include         temperature, pressure, and catalyst. Some examples include:         -   i. Halogenating ethane so that it contains mixed halides             including 1,1 and 1,2-dihaloethanes. Dehyrohalogenating the             dihaloethanes, and rehydrohalogenating to enrich the             1,2-dihaloethane content.         -   ii. Halogenating propane so that it contains mixed halides             including 1,1, 2,2, 1,3, and 1,2-dihalopropanes.             Dehyrohalogenating the dihalopropanes, and             rehydrohalogenating to enrich the 1,2-, 2,2-, 1,3, or             1,1-isomer content.         -   iii. Halogenating butane so that it contains mixed             dihalides. Dehyrohalogenating, and rehydrohalogenating to             enrich the 2,2- or 2,3-isomer content. The 2,2- or             2,3-isomer may be reacted with a metal oxide to make             methyl-ethyl ketone.         -   iv. Halogenating butane so that it contains mixed             tetrahalides. Dehyrohalogenating, and rehydrohalogenating to             enrich the 1,2,3,4-isomer content.         -   v. Halogenating cyclohexane so that it contains mixed             halides including 1,1, 1,2, 1,3, and 1,4-dihaloisomers.             Dehyrohalogenating, and rehydrohalogenating to enrich the             1,1, 1,2, 1,3, and 1,4-dihaloisomer content.

2. Enrichment in the primary halide content of a stream of mixed halide isomers by separating primary halides from other halide isomers. Dehydrohalogenating the other isomers, rehydrohalogenating the resulting olefins to produce a stream enriched in primary halide isomers, and returning the resulting stream to the primary halide separation step. Some variations include:

-   -   a. Using selective dehydrohalogenation of the non-primary         isomers to form easily separated olefin and hydrogen halide.     -   b. Using distillation to separate the primary and other isomers.     -   c. Using adsorption to separate the primary and other isomers.     -   d. Using a shape-selective catalyst to rehydrohalogenate the         olefin, enhancing primary halide yield.

3. The use of multiple halogens to create the desired halide isomer. One halogen may be used to halogenate the hydrocarbon and be replaced by another.

4. The use a membrane reactor with halogen on one side and alkane on the other to improve selectivity to the desired halide isomer. This reactor design may improve monohalogenation, dihalogenation, and/or primary halogenation selectivity.

5. Operation of the halogenation reaction at high halogen:alkane ratio to improve conversion may result in unconverted halogen. Photoactivation of the unconverted halogen may be used at low temperature in a solid oxide bed to allow full recovery of all the halogen.

Improvements to the Reproportionation Step

In many processes, the overhalogenated species may be recycled to a point in the process where they are converted to the desired degree of halogenation or less than the desired degree of halogenation. The change in degree of halogenation is termed “reproportionation,” and allows for the use of the carbon and hydrogen in the overhalogenated species, thus reducing feedstock loss and perhaps also allowing greater economic per-pass yield.

Several Improvements Include:

1. A low-temperature reproproportionation step, in which the halogen is redistributed among over-halogenated species, resulting in the formation of optimally halogenated species and additional very highly halogenated species.

-   -   a. An example is a mixture of dibromomethane, tribromomethane,         and tetrabromomethane are allowed to react, producing a stream         enriched in methyl bromide and tetrabromomethane.

2. A low-temperature reproproportionation step, in which the halogen is redistributed among over-halogenated species, resulting in the formation of optimally halogenated species and additional very highly halogenated species. The yield of optimally halogenated species is maximized by conducting this reproportionation under temperature, pressure, and process conditions such that the reproportionation is conducted in the liquid phase while the optimally halogenated species is predominantly in the vapor phase.

-   -   a. An example is: a mixture of liquid dibromomethane,         tribromomethane, and tetrabromomethane are allowed to react in         the presence of a catalyst at about 30 C. As the bromine is         redistributed and methyl bromide is formed, much of the methyl         bromide leaves the solution and enters the vapor phase.

3. The conversion of over-halogenated hydrocarbon to carbon black or other carbon material and halogen. The carbon material may be sold and the halogen may be recycled to the process.

4. The reproportionation of overhalogenated hydrocarbon with another hydrocarbon or halohydrocarbon. Such a process may allow the recovery of the desired hydrocarbon with a loss of a less desirable material.

-   -   a. For example, dibromomethane is reacted with propane to make         methyl bromide and brominated propanes. Ideally, one propane         molecule can be used to convert eight dibromomethane molecules         to methyl bromide. The bromine can be recovered from the         brominated propane through thermal decomposition, oxidation,         reaction with solid oxide, or other means.         Improvements to the Solid Oxide Reaction

1. A method of contacting water with alkyl halide and metal oxide in a multi-phase reactor with alkyl halide, solid oxide and optional diluent present at the bottom of the reactor with refluxing water present in a zone above the reactant mixture.

2. The product yield may be increased and process corrosivity may be reduced by conducting the solid oxide reaction in a liquid phase with water present to remove metal halide as it is formed. A specific example is:

-   -   a. The reaction is conducted in a vessel containing liquid alkyl         halide, liquid water, water vapor, and solid. The water vapor         condenses at the top of the reactor or is returned from an         external condenser and settles through the metal oxide and alkyl         halide containing phase. The water dissolves metal halide as it         passes through the alkyl halide phase. The solid oxide may be         supported on a plate to keep it out of the liquid water phase.         The water and metal halide passes into a separate liquid phase         at the bottom of the reactor where some of the water is         vaporized. Variations include:         -   i. A batch reactor.         -   ii. A continuous reactor in which alkyl halide, metal oxide,             and water (or steam) are added continuously and metal halide             solution is removed continuously to a regeneration reactor             where it is dried and regenerated.         -   iii. The use of precipitation to remove metal halide from             the metal halide solution. By reducing the temperature of             the solution, some of the metal halide will precipitate for             regeneration. The depleted metal halide solution may be             recovered by filtration, centrifugation or other             solids-liquid separation methods and recycled to the             reactor. Recovered solids can be dried and regenerated to             metal oxide and bromine.

3. The liquid phase performance of a reactor may be improved by adding a diluent. The diluent may be, but is not limited to alkanes that are readily separated from the products and reactants.

4. The yield to desired product may be improved by introducing the stream containing hydrocarbon halide to the metal oxide in stages.

5. The yield to desired product may be improved by providing a feed of solid to a fluidized bed reactor that includes some partially or completely spent material. Spent is defined as solid with no remaining oxygen (donation) capacity or bromine capacity.

6. The yield to desired product may be improved by providing a feed of solid to a fluidized bed reactor that includes some partially coked material.

7. The solid oxide reaction may be conducted in a series of switched fixed beds, some of which are undergoing regeneration at any given time.

8. In a process for the production of olefins, the di-halogenated species may be at least partially converted to olefin using certain solids. Some examples include:

-   -   a. The reaction of silver metal with 1,2-dibromoethane to form         ethylene and silver bromide. The silver bromide may be         decomposed to silver and bromine using heat or electromagnetic         radiation.     -   b. The reaction of copper (I) bromide with 1,2-dibromethane to         form ethylene and copper(II) bromide. The copper (II) bromide         may be decomposed to copper (I) bromide and bromine using heat.     -   c. The reaction of 1,2-dibromomethane with a metal oxide to form         ethylene, carbon dioxide, water, and metal bromide. The metal         bromide may be regenerated by reaction with oxygen.

Improvements to Solid Oxide Regeneration

1. Varying the temperature of solid oxide prior to oxygen introduction to change the particle size of the solid oxide to a more desirable distribution.

-   -   a. By raising the temperature, particularly to that above the         regeneration onset temperature, prior to introduction of oxygen         or air, the metal oxide obtained after regeneration may be         reduced in the amount of fines or agglomerates it contains.     -   b. By introducing oxygen at low temperature, particularly at         that below the regeneration onset temperature, the metal oxide         obtained after regeneration may be reduced in the amount of         fines or agglomerates it contains.

2. Increasing the temperature of solid oxide prior to oxygen introduction to dehydrogenate or desorb adsorbed hydrocarbon, reducing the amount of water and possibly carbon oxides generated in regeneration, thus reducing corrosivity and simplifying halide purification.

3. Performing a separate oxidation, particularly at low temperature, to remove adsorbed hydrocarbon reducing the amount of water and carbon oxides generated in regeneration, thus reducing corrosivity and simplifying halide purification.

4. Introducing water to the solid halide to change the particle size of the resulting solid oxide to a more desirable distribution.

-   -   a. The water may be introduced in the gas phase.     -   b. The water may be introduced in the liquid phase.     -   c. The water may be introduced concurrently with or prior to the         introduction of oxygen.     -   d. The hydrated solid may be allowed to settle and agglomerate.     -   e. The hydrated solid may be subjected to intense fluidization         to break apart agglomerates.     -   f. A slurry or aqueous phase may be formed and dried in a manner         to form the desired particle size. In particular, spray drying         may be used.

5. Dissolving the active metal halide to separate it from impurities, and then converting metal halide to metal oxide.

6. The use of very high temperature regeneration to remove impurities. In particular, chlorine may be removed from metal bromide in this manner.

a. The combination of high temperature with heating of the solid halide prior to oxygen introduction may be particularly useful. In the case of metal bromides, this methodology may allow the removal of chlorine as C1Br or C1₂.

7. The reduction of the solid halide with hydrogen or other reducing agent to remove impurities. The reduced material may be reoxidized with oxygen, air, or other oxygen containing gas.

Improvements in Separations

1. Separation of halogen from nitrogen, oxygen, and other non-condensibles using solid adsorbents. The solid adsorbents will adsorb the halogen, which can be removed by heating the solid or reducing the pressure. The adsorbents may be, but are not limited to:

-   -   a. Molecular sieves;     -   b. Mesoporous materials;     -   c. Zeolites;     -   d. Silica;     -   e. Alumina;     -   f. Aluminosilicates;     -   g. Magnesia;     -   h. Activated carbon;     -   i. Metal bromides;     -   j. Metal oxides;

2. Separation of halogen from nitrogen, oxygen, and other non-condensibles using reactive solid adsorbents. The solid reactive adsorbents will react with the halogen, forming a new chemical composition, from which the halogen can be removed by heating the solid or reducing the pressure, regenerating the solid. The reactive adsorbents may be, but are not limited to:

-   -   a. Copper (I) bromide;     -   b. Iron (II) bromide;     -   c. Silver bromide;     -   d. Carbon;     -   e. Carbon, particularly fullerenes or nano-tubular carbon.

3. Removal of water from halogen by passing the mixed stream over metal halides or metal halide hydrates which may be supported or unsupported. The metal halides will form hydrates and the metal halide hydrates will form more highly hydrated species. The water can be liberated and starting material can be regenerated by heating.

4. Methods of removing trace amounts of halogen from product streams using reactive solids, which may or may not be regenerable. Some specific reactive solids include, but are not limited to:

-   -   a. Copper (II) oxide;     -   b. Silver;     -   c. Copper;     -   d. Lithium;     -   e. Magnesium;     -   f. Alkali metals.

5. Removal of residual halogen from streams by reaction with olefins. Specific examples include:

-   -   a. Reacting with ethylene or propylene to form dihaloalkane,         which can be converted to epoxide.     -   b. Reacting with a heavy multiple-olefin to form highly         halogenated species from which the halide can be recovered.

6. Removal of residual hydrocarbon halide from streams by reaction with reactive solids Some specific reactive solids include, but are not limited to:

-   -   a. Copper (II) oxide;     -   b. Silver;     -   c. Copper;     -   d. Lithium;     -   e. Magnesium;     -   f. Alkali metals.

7. Separation of primary, secondary, and/or tertiary alkyl halides by selective dehydrohalogenation of selected species, separation of the olefin and hydrogen halide from the remaining alkyl halide, and recombination of the hydrogen halide and olefin to form alkyl halides. Examples include, but are not limited to:

-   -   a. Separation of primary from secondary alkyl halides by         selectively dehydrohalogenating the secondary alkyl halides to         olefin and hydrogen halide, separation of the olefin and         hydrogen halide from the primary halide, and recombination of         the hydrogen halide and olefin to form secondary and possibly         primary halide.     -   b. Separation of primary and secondary alkyl halides from         tertiary alkyl halides by selectively dehydrohalogenating the         tertiary alkyl halides to olefin and hydrogen halide, separation         of the olefin and hydrogen halide from the primary and secondary         alkyl halide, and recombination of the hydrogen halide and         olefin to form alkyl halide.

8. Removal of sulfur-containing compounds from a hydrocarbon feed by reacting the feed with dry halogen to form sulfur, which can be removed as a solid from the sulfur-depleted hydrocarbon and hydrocarbon halide stream.

9. Removal of sulfur-containing compounds from a hydrocarbon feed by reacting the feed with dry halogen to form sulfur, which can be removed as a solid from the sulfur-depleted hydrocarbon and hydrocarbon halide stream.

10. Removal of carbon dioxide from a stream by reacting with a carbonate-forming material such as calcium oxide. The carbonate may be used in a hydrogen-halide recovery section of the plant. The carbonate will react with hydrogen halide, liberating water and carbon dioxide and producing solid halide, which can be regenerated and recycled to the carbon dioxide separation section.

11. Removal of arsenic, mercury, heavy metal-containing compounds from a hydrocarbon feed by reacting the feed with dry halogen to form solid metal compounds, solid metal halides or halogenated metal hydrocarbons, which can be easily separated.

12. Removing adsorbed product from the solid by rinsing with a compound that is easily separated from the product. Such a rinsing agent may be pentane or other alkane.

13. Removing adsorbed product from the solid by steam distillation.

Maintenance

1. A method of removing coke from reactors by reacting with bromine to form volatile carbon bromides. The carbon bromides may be used in the process in a reproportionation step, thus producing product from the coke.

2. A method of removing coke from reactors by reacting with hydrogen bromide to form volatile hydrocarbon bromides. The carbon bromides may be used in the process in a reproportionation step, thus producing product from the coke.

Start-Up

1. Starting the process with some or all of the solid in the halide or partially halogenated form may provide a number of benefits including:

-   -   a. The ability to start the regeneration reactor early in the         start up sequence.     -   b. Reduction in the amount of oxygen carried over into the         bromine separation unit.     -   c. Reduction in the heat generated in the metal oxide reactor or         hydrogen halide neutralization step.     -   d. Reduction in the amount of adsorbed hydrocarbon and thus         reduction in the amount of water and carbon dioxide generated in         the regeneration unit.     -   e. Reduction in unfavorable changes in the particle size         distribution of the metal oxide.     -   f. Improvement in the packing of a fixed bed reactor.     -   g. Providing a hygroscopic metal halide to reactively remove         water during upsets.

2. Starting the process with some or all of the solid in the oxide or partially oxygenated form may provide a number of benefits including:

-   -   a. The ability to start the solid oxide reactor early in the         start up sequence.     -   b. Reduction in the amount of bromine generated in the         regeneration reactor.     -   c. Reduction in the heat generated in the metal oxide reactor or         hydrogen halide neutralization step.     -   d. Reduction in the amount of adsorbed hydrocarbon and thus         reduction in the amount of water and carbon dioxide generated in         the regeneration unit.     -   e. Reduction in unfavorable changes in the particle size         distribution of the metal     -   f. Improvement in the packing of a fixed bed reactor.     -   g. Providing a hygroscopic metal halide to reactively remove         water during upsets.

3. Starting the process with a solid which has undergone a number of regeneration cycles may offer benefits including:

-   -   a. Reduction in byproducts.     -   b. Improved chemical and thermal stability of reactors

4. Starting the process with the halogen present in part or completely as alkyl halide may be desirable for a number of reasons including:

-   -   a. Less free halogen present during start-up.     -   b. Ability to start the halide separations section early in the         start-up sequence with no hydrogen halide or water present.         Shut-Down

1. Stopping the process with the halide in metal halide and/or alkyl halide form may improve safety, reduce corrosion, and improve maintenance accessibility.

2. Introducing reactive components into certain sections of the plant may provide a sink for halogen or hydrogen halide, improving safety, reducing corrosion and improving accessibility. An example of such a component is olefin.

Materials of Construction

1. The reactors for alkane halogenation and metathesis consisting of materials to minimize corrosion including but not limited to:

-   -   a. Stainless steel;     -   b. Silicon carbide;     -   c. Glass lined steel;     -   d. Titanium;     -   e. Carbon fiber.

2. Process components operating at temperatures below 300 C. constructed from:

-   -   a. Teflon;     -   b. Glass. 

What is claimed is:
 1. A method comprising: providing a first quantity of alkane; providing a quantity of bromine; reacting the first quantity of alkane with the quantity of bromine to form alkyl monobromides, hydrogen bromide, and alkyl polybromides; providing a second quantity of alkane; reacting the second quantity of alkane with the alkyl polybromides to form additional alkyl monobromides; reacting the alkyl monobromides and the additional alkyl monobromides with a metal oxide to form a metal bromide and at least one reaction product selected from the group consisting of an alcohol and an ether; contacting the metal bromide with oxygen or air to regenerate the metal oxide and to form bromine; and recycling the bromine.
 2. The method of claim 1 wherein the first and second quantities of alkane comprise at least one alkane selected from the group consisting of methane, ethane, propane, butane, and isobutane.
 3. The method of claim 1 wherein the first and second quantities of alkane comprise methane.
 4. The method of claim 1 wherein the alkyl polybromides comprise CH₂Br₂. and the alkyl monobromides comprise CH₃Br.
 5. The method of claim 1 wherein the reaction product comprises methanol.
 6. The method of claim 1 wherein the reaction product comprises dimethyl ether.
 7. The method of claim 1 wherein the alkyl monobromides and the additional alkylmonobromides are reacted with hydrogen bromide and the metal oxide to form the metal bromide and the at least one reaction product.
 8. The method of claim 1 wherein the second quantity of alkane is reacted with the alkyl polybromides in the presence of an electrophilic catalyst.
 9. A method comprising: providing a first quantity of alkane; providing a quantity of bromine; reacting the first quantity of alkane with the quantity of bromine to form alkyl monobromides, hydrogen bromide, and alkyl polybromides; providing a second quantity of alkane; reacting the second quantity of alkane with the alkyl polybromides to form additional alkyl monobromides; reacting the alkyl monobromides and the additional alkyl monobromides with a metal oxide to form a metal bromide and at least one reaction product selected from the group consisting of an alcohol, an ether, and an olefin; contacting the metal bromide with oxygen or air to regenerate the metal oxide and to form bromine; and recycling the bromine.
 10. The method of claim 9 wherein the first and second quantities of alkane comprise at least one alkane selected form the group consisting of methane, ethane, propane, butane, isobutane, pentane, hexane, and cyclohexane.
 11. The method of claim 9 wherein the first and second quantities of alkane comprise methane.
 12. The method of claim 9 wherein the alkyl polybromides comprise at least one alkyl polybromide selected from the group consisting of CH₂Br₂, CHBr₃, and CBr₄ and wherein the alkyl monobromides comprise CH₃Br.
 13. The method of claim 9 wherein the reaction product comprises methanol.
 14. The method of claim 9 wherein the reaction product comprises dimethyl ether.
 15. The method of claim 9 wherein the first and second quantities of alkane comprise two or more carbon atoms in their molecular structure and the reaction product comprises an olefin.
 16. The method of claim 9 wherein the first and second quantities of alkane comprise ethane and the reaction product comprises at least one reaction product selected from the group consisting of diethyl ether, ethanol, and ethyl acetate.
 17. The method of claim 9 wherein the alkyl monobromides and the additional alkylmonobromides are reacted with hydrogen bromide and the metal oxide to form the metal bromide and the at least one reaction product.
 18. The method of claim 9 wherein the second quantity of alkane is reacted with the alkyl polybromides in the presence of an electrophilic catalyst.
 19. A method comprising: providing a first quantity of alkane; providing a quantity of halogen; reacting the first quantity of alkane with the quantity of halogen to form alkyl monohalides, hydrogen halide, and alkyl polyhalides; providing a second quantity of alkane; reacting the second quantity of alkane with the alkyl polyhalides to form additional alkyl monohalides; reacting the alkyl monohalides and the additional alkyl monohalides with a metal oxide to form a metal halide and at least one reaction product selected from the group consisting of an alcohol, an ether, and an olefin; contacting the metal halide with oxygen or air to regenerate the metal oxide and to form halogen; and recycling the halogen.
 20. The method of claim 19 wherein the halogen comprises at least one halogen selected form the group consisting of chlorine, bromine, and iodine. 